In the field of toners for electrophotography, it has been demanded to develop toners having a smaller particle size and an excellent fusing property in view of achieving higher image qualities. Conventional processes for producing the toners include a melt-kneading and pulverization method, and a wet process such as an emulsification and aggregation method. In these methods, resin binders, for example, those composed mainly of a polyester, are used to obtain toner particles.
Conventionally, upon producing a crosslinked polyester as the resin binder, a trivalent or higher valent polycarboxylic acid such as trimellitic acid has been used as a raw crosslinking component thereof. For example, JP 6-19204A discloses the toner using such a polyester produced from a monomer composition composed of an aromatic dicarboxylic acid component selected from isophthalic acid, terephthalic acid and derivatives thereof, an aromatic tricarboxylic acid component selected from trimellitic acid and derivatives thereof, a dicarboxylic acid component selected from dodecenylsuccinic acid, octylsuccinic acid and anhydrides thereof, and a propoxylated and/or ethoxylated etherified diphenol component.